| 1 | #!/usr/bin/python |
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| 2 | |
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| 3 | import sys, struct, logging |
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| 4 | from .value import Value |
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| 5 | |
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| 6 | # initialize logger |
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| 7 | logger = logging.getLogger(__name__) |
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| 8 | |
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| 9 | class Attribute(object): |
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| 10 | """ |
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| 11 | In addition to what the RFC reports, an attribute has an |
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| 12 | 'attribute tag', which specifies what type of attribute it is. |
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| 13 | It is 1 bytes long, and comes before the list of values. |
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| 14 | |
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| 15 | From RFC 2565: |
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| 16 | |
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| 17 | Each attribute consists of: |
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| 18 | ----------------------------------------------- |
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| 19 | | value-tag | 1 byte |
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| 20 | ----------------------------------------------- |
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| 21 | | name-length (value is u) | 2 bytes |
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| 22 | ----------------------------------------------- |
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| 23 | | name | u bytes |
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| 24 | ----------------------------------------------- |
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| 25 | | value-length (value is v) | 2 bytes |
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| 26 | ----------------------------------------------- |
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| 27 | | value | v bytes |
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| 28 | ----------------------------------------------- |
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| 29 | |
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| 30 | An additional value consists of: |
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| 31 | ----------------------------------------------------------- |
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| 32 | | value-tag | 1 byte | |
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| 33 | ----------------------------------------------- | |
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| 34 | | name-length (value is 0x0000) | 2 bytes | |
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| 35 | ----------------------------------------------- |-0 or more |
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| 36 | | value-length (value is w) | 2 bytes | |
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| 37 | ----------------------------------------------- | |
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| 38 | | value | w bytes | |
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| 39 | ----------------------------------------------------------- |
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| 40 | """ |
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| 41 | |
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| 42 | def __init__(self, name=None, values=None): |
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| 43 | """ |
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| 44 | Initialize an Attribute. This function can be called in three |
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| 45 | different ways: |
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| 46 | |
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| 47 | Attribute() -- creates an empty Attribute |
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| 48 | |
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| 49 | Attribute(name) -- creates an empty Attribute with a name |
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| 50 | |
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| 51 | Attribute(name, values) -- creates an Attribute |
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| 52 | initialized with a name and list of values |
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| 53 | |
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| 54 | Arguments: |
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| 55 | |
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| 56 | name -- the name of the attribute |
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| 57 | |
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| 58 | values -- a list of Values. May not be empty. |
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| 59 | """ |
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| 60 | |
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| 61 | if name is not None: |
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| 62 | assert isinstance(name, str), \ |
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| 63 | "Attribute name must be a string!" |
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| 64 | if values is None: |
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| 65 | values = [] |
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| 66 | for value in values: |
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| 67 | assert isinstance(value, Value), \ |
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| 68 | "Value %r must be of type Value" % (value) |
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| 69 | |
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| 70 | self.name = name |
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| 71 | self.values = values |
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| 72 | |
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| 73 | @property |
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| 74 | def packed_value(self): |
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| 75 | """ |
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| 76 | Packs the attribute data into binary data. |
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| 77 | """ |
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| 78 | |
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| 79 | assert self.name is not None, \ |
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| 80 | "cannot pack unnamed attribute!" |
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| 81 | assert len(self.values) > 0, \ |
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| 82 | "cannot pack empty attribute!" |
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| 83 | |
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| 84 | # get the binary data for all the values |
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| 85 | values = [] |
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| 86 | for v, i in zip(self.values, xrange(len(self.values))): |
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| 87 | |
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| 88 | # get the name length (0 for everything but the first |
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| 89 | # value) |
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| 90 | if i == 0: |
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| 91 | name_length = len(self.name) |
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| 92 | else: |
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| 93 | name_length = 0 |
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| 94 | |
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| 95 | # get the value length and binary value |
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| 96 | value_bin = v.packed_value |
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| 97 | value_length = len(value_bin) |
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| 98 | |
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| 99 | logger.debug("dumping name_length : %i" % name_length) |
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| 100 | logger.debug("dumping name : %s" % self.name) |
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| 101 | logger.debug("dumping value_length : %i" % value_length) |
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| 102 | logger.debug("dumping value : %s" % v.value) |
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| 103 | |
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| 104 | # the value tag in binary |
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| 105 | value_tag_bin = struct.pack('>b', v.value_tag) |
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| 106 | |
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| 107 | # the name length in binary |
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| 108 | name_length_bin = struct.pack('>h', name_length) |
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| 109 | |
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| 110 | # the name in binary |
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| 111 | name_bin = self.name |
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| 112 | |
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| 113 | # the value length in binary |
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| 114 | value_length_bin = struct.pack('>h', value_length) |
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| 115 | |
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| 116 | if i == 0: |
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| 117 | values.append(''.join([value_tag_bin, |
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| 118 | name_length_bin, |
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| 119 | name_bin, |
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| 120 | value_length_bin, |
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| 121 | value_bin])) |
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| 122 | else: |
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| 123 | values.append(''.join([value_tag_bin, |
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| 124 | name_length_bin, |
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| 125 | value_length_bin, |
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| 126 | value_bin])) |
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| 127 | |
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| 128 | # concatenate everything together and return it along with the |
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| 129 | # total length of the attribute |
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| 130 | return ''.join(values) |
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| 131 | |
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| 132 | @property |
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| 133 | def packed_value_size(self): |
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| 134 | """ |
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| 135 | Gets the total size of the attribute. |
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| 136 | """ |
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| 137 | return len(self.packed_value) |
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| 138 | |
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| 139 | total_size = packed_value_size |
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| 140 | |
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| 141 | def __str__(self): |
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| 142 | if len(self.values) > 0: |
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| 143 | values = [str(v) for v in self.values] |
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| 144 | else: |
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| 145 | values = "None" |
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| 146 | |
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| 147 | if self.name is None: |
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| 148 | name = "None" |
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| 149 | else: |
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| 150 | name = self.name |
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| 151 | |
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| 152 | return "%s: %s" % (name, str(values)) |
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| 153 | |
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| 154 | def __repr__(self): |
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| 155 | return '<IPPAttribute (%r, %r)>' % (self.name, self.values) |
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